Significance of De Ritis (Aspartate Transaminase/Alanine Transaminase) Ratio as a Significant Prognostic But Not Predictive Biomarker in Japanese Patients with Metastatic Castration-resistant Prostate Cancer Treated with Cabazitaxel

Background/Aim: To date, there have not been any established biomarkers predicting the efficacy of cabazitaxel in patients with metastatic castration-resistant prostate cancer (mCRPC). The objective of this study was to evaluate the significance of the aspartate aminotransaminase (AST)/alanine aminotransaminase (ALT) ratio (De Ritis ratio) as a biomarker for mCRPC patients receiving cabazitaxel. Patients and Methods: This study included 74 consecutive docetaxel-refractory mCRPC patients treated with cabazitaxel. It assessed the impact of the pretreatment De Ritis ratio, in addition to conventional clinicopathological parameters, on the oncological outcomes in these patients. Results: After treatment with cabazitaxel, 22 (29.7%) of the 74 patients achieved a prostate-specific antigen (PSA) response; however, there was no significant difference in the PSA response rate between patients with a low De Ritis ratio (<1.35) and those with a high ratio (>= 1.35). In this series, the median periods of PSA progression free survival (PFS) and overall survival (OS) after the introduction of cabazitaxel were 4.2 and 14.7 months, respectively. No significant difference was noted in PSA PFS between the low and high De Ritis ratio groups, whereas OS in the high De Ritis ratio group was significantly poorer compared with that in the low De Ritis ratio group. Univariate analysis showed the significant impact of the De Ritis ratio on OS, but not PFS, in these 74 patients. Furthermore, the De Ritis ratio, in addition to the performance status and lactate dehydrogenase level, was shown to be independently associated with OS on multivariate analysis. Conclusion: Assessment of the De Ritis ratio may provide useful prognostic, but not predictive, information on cabazitaxel therapy in mCRPC patients.